Electrocoagulation Water Treatment Explained

Electrocoagulation water process

Electrocoagulation works by passing contaminated water between a pair of electrodes that makeup a cell.  Electrodes are either aluminum or steel, depending on the water being treated.  As water passes between the two electrodes, electricity is conducted through the water and the metal ions are liberated from the surface of the anode (Positive), forming metal hydroxides in solution.  These charged metal hydroxides attach themselves to contaminants in the water and within 30 seconds to 2 minutes after the water exits the cell, coagulation occurs.  

The coagulated solids are now large enough to be filtered and dense enough to settle with the exception of emulsified oil that will float to the surface.  The electrocoagulation generated solids can then be separated from the treated water by settling, use of dissolved air flotation, or filtration, leaving the clarified or filtered water suitable for discharge, or reuse.  Many applications require further removal of dissolved solids from the filtered water not removed by electrocoagulation, such as sodium chloride.  In those cases, electrocoagulation provides an excellent pre-treatment technology to remove contaminants prior to reverse osmosis to prevent blinding of the membrane.  

Electrocoagulation History

Electrocoagulation “EC” was discovered in the early 1900‘s and was thought to be the ultimate answer to water treatment. However, available technology was simply unable to implement its full potential. It was not until the late 1980‘s that the state of the art reached a point where it was viable for large-scale deployment.

Today, EC equipment is available through only a handful of vendors worldwide and many of these products are crude, costly to operate and maintain and unsuitable for industrial use.

The EC process destabilizes suspended, emulsified or dissolved contaminants in an aqueous medium by introducing an electrical current into the medium. The electrical current provides the electromotive force to drive oxidation/reduction chemical reactions. The anodes consisting of either steel or aluminum material are consumed by way of electrolytic oxidation that forms a metal hydroxide coagulant.  This coagulant, along with electrostatic effects within the reaction medium produce solids that are either less colloidal or less emulsified (or soluble) than the compounds prior to electrochemical intervention.

As these phenomena occur, the contaminants form hydrophobic entities precipitate and can easily be removed by a number of secondary separation techniques. EC essentially utilizes direct current to cause sacrificial electrode oxidation to produce cations to precipitate, co-precipitate or even oxidize undesirable contaminants and/or by causing colloidal materials to coalesce and then be removed by electrolytic flotation.

The electrochemical system has proven to be viable with a wide variety of wastewater including oily/petrol industry streams, paper pulp mill waste, metal plating, tanneries, dye/textile, food processing, canning factories, steel mill effluent, slaughterhouses, chromium, lead, and mercury-laden effluents, arsenic, hardness/scale component bearing streams, as well as domestic sewage. Frequently, especially for sewage, the treated water effluent will be better than the raw water from which it originated.

Electrocoagulation Capabilities - Up To 99.9% Contaminant Removal

Electrocoagulation is the distinct economic and environmental choice for meeting water treatment discharge standards and compliance requirements. Capital and operating costs are generally recovered by eliminating discharge fees and fines, harvesting resources, and significantly reducing water replacement costs.

  • Removes heavy metals as oxides that pass TCLP
  • Removes suspended and colloidal solids.
  • Breaks oil emulsions in water.
  • Removes fats, oil, and grease.
  • Destroys & removes bacteria, viruses & cysts.
  • Processes multiple contaminants in one step.

Key Applications

  • Ground water cleanup.
  • Oil and gas production water treatment and recovery
  • Process rinse and wash water.
  • Sewage treatment.
  • Pretreatment for reverse osmosis, ultra filtration, nanofiltration.
  • Industrial wastewater.

 Benefits

  • Low capital costs.
  • Low operating costs.
  • Low power requirements.
  • Generally no chemical additions.
  • Metal oxide formation passing TCLP.
  • Low maintenance.
  • Minimal operator attention.
  • Sludge minimization.
  • Treats multiple contaminants.

Electrocoagulation is most suitable for total suspended solids, bacteria, heavy metals, silica, free oil, and emulsified oil.  Electrocoagulation is important for use in O&G drill water make up and completion water/fluids makeup. Complete elimination of bacteria will provide the service company in either situation with water free of sulfate reducing bacteria “SRB” for introduction into the drilled reservoir or completion zone.

Oil & Gas Flowback Water-

The image below shows flowback water (left beaker) that is contaminated with bacteria, causing it to turn black in appearance.  The beaker on the right is a few minutes after the water was treated with electrocoagulation and subjected to oxidation.

Oil & Gas Produced Water-

The below image represents treatment of produced water at 350,000 microsiemens conductivity.  The bottle on the left is immediately following electrocoagulation, and the bottle on the right is after electrocoagulation and 3 minutes of settling time.